'I have seen the technology and it works' ... former US secretary of state Colin Powell, who is on the board of Bloom Energy. Photograph: Stefan Zaklin/AFP/Getty

A new technology that its creator claims can be an off-grid source of cheap, clean electricity in a device the size of a loaf of bread is about to get its close-up.

The formal debut of Bloom Energy's much-hyped fuel cell, known as the Bloom Box, will take place at eBay's headquarters in California on Wednesday, and will reportedly attract figures from the former secretary of state, Colin Powell, who is on the company's board, to the state's governor, Arnold Schwarzenegger.

The anticipation can be gauged by a segment on the CBS network's flagship television programme, 60 Minutes, on Sunday which talked about the "holy grail" of clean energy technology. A clock on Bloom Energy's website – which contains little information bar an inspirational video of astronauts and of winning runners cresting the tape at the finish line – counts down the minutes until the launch.

Venture capitalists have reportedly poured $400m into Bloom Energy's project since founder KR Sridhar began his work eight years ago. Twenty companies, including Wal-Mart and Google, are trying out the device. Sridhar has also attracted the high-profile support of Powell, who proclaimed last year: "I have seen the technology and it works."

But industry watchers say they remain unsure exactly how it works. They also say Sridhar has aroused suspicion with his secretive approach, which includes working in an HQ with no sign outside.

Scientists and entrepeneurs have been trying for years to create a low-cost option for generating and storing fuel. Sridhar has told reporters his work draws on his research on generating oxygen for Nasa's missions to Mars. The Bloom Box allegedly reverses this process, using natural gas or plant waste as fuel while producing relatively little carbon dioxide.

Sridhar gave CBS the first glimpse of the technology, explaining that the boxes are produced from stacks of ceramic plates. The plates, which are made of sand, are painted with special green and black inks. He declares that one such stack, or cell, can power a light bulb; 64 can power a coffee shop.

Nasa has been using similar devices aboard its vehicles for years but Sridhar's achievement was to make the technology affordable, he told the Atlantic magazine last December.

He has been running a pilot project of the technology at the University of Tennessee for the last two years, where the Bloom Box reportedly proved twice as efficient as traditional power sources and produced 60% fewer emissions.

But its real potential lies in its claimed ability to use any fuel source – gas, plants, wind, solar, etc – to generate power, which would theoretically enable the Bloom Box to operate entirely off the electricity grid. That would offer developing countries, such as Sridhar's native India, the chance to provide cheap, clean electricity to remote villages.

"I want to open up access to energy the way that PCs and the web opened up access to information," Sridhar told the Atlantic. "So people can live where they want, and still be connected, without someone telling them when they can do their laundry."